Lecture 18 © slg Chemistry 151

Review, Electronic Configuration of Atoms• Electronic Configuration of Ions• Magnetism

TOPICS:

Review, Electronic Configuration of Atoms

Let’s start by doing a complete set of configurations for lead, Pb, Z= 82

The first step: find element in periodic table noting: a) which block (s, p, d, f) b) which period c) which column

Pb , Z =82, 6th period, Column 4A

1s 1s

2s 2s 2p 2p 2p 2p 2p 2p

3s 3s 3p 3p 3p 3p 3p 3p

4s 4s 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 4p 4p 4p 4p 4p 4p

5s 5s 4d 4d 4d 4d 4d 4d 4d 4d 4d 4d 5p 5p 5p 5p 5p 5p

6s 6s 4f 5d 5d 5d 5d 5d 5d 5d 5d 5d 5d 6p 6p 6p 6p 6p 6p

7s 7s 5f

6p2

1A 2A 3A 4A 5A 6A 7A 8A

Period 6

Period 1

Pb, Z= 82

p block

6th period

Column 4A

“6p2”

Locates shell (n# for s,p = period #)

Locates last e in place in orbital

6p 6p 6p

Places last e in subshell

1s2 )2 2s2 2p6 )10 3s2 3p6 )18 4s2 3d10 4p6 )36

5s2 4d10 5p6 )54 6s2 5d1 4f14 5d9 6p2 )82

4f145d10 summarize!

Short, order of filling:

Xe54 6s2 4f14 5d10 6p2

Short, order of shells: Xe54 4f14 5d10 6s2 6p2

Four outer shell, valence electrons; group 4A;once the inner shell d’s and f’s are full: core electrons

Long form, order of filling, from PT:

Group Work:

Ag, Z= 47 Short: Order of Filling Short: Order of Shells

Sb, Z= 51 Short: Order of Filling Short: Order of Shells

Rf, Z= 104 Short: Order of Filling Short: Order of Shells

Circle valence electrons in short form, order of shells

Key:

Ag, Z= 47 Short, Order of Filling: [Kr36] 5s24d9 5s14d10 Short, Order of Shells: [Kr36] 4d9 5s2 4d10 5s1

Sb, Z= 51 Short: Order of Filling [Kr36] 5s2 4d10 5p3

Short: Order of Shells [Kr36] 4d10 5s2 5p3

Rf, Z= 104 Short: Order of Filling [Rn86] 7s2 5f14 6d2 Short: Order of Shells [Rn86] 5f14 6d2 7s2

Electronic Configuration of Ions

The electronic configurations we have developedgive the basis for the charges we have alreadyassigned to many elements when they are found asions in an ionic type compound.

The main group elements (columns 1A-8A) lose, gainor share valence electrons in forming compounds so that they can achieve an outer shell configuration,when possible, of the nearest noble gas.

When electrons are transferred from one element toanother, charged particles called ions are formed.

We have already assigned a positive charge, equal tothe column number, for ions formed from elements in columns 1A, 2A and selected 3A elements.

Note how this correlates with configurations we have done:

Na, Z=11, Column 1A, +1 cation:

1s2 2s2 2p6 3s1-1e

1s 2 2s 2 2p6 Neon configuration Na +

Column 1A: All Ions, +1

H Z=1 1s1 H 1+

Li Z=3 He2 2s1 Li 1+ He2

Na Z=11 Ne10 3s1 Na 1+ Ne10

K Z=19 Ar18 4s1 K 1+ Ar18

Rb Z= 37 Kr36 5s1 Rb 1+ Kr36

Cs Z= 55 Xe54 6s1 Cs 1+ Xe54

Fr Z= 87 Rn86 7s1 Fr 1+ Rn86

Nearest noble gas

Since all 1A elements share the same outer shellconfiguration, “s1”, they are all expected to form the same charged ion, +1.

All elements in column 2A, with the outer shell configuration of “s2” show a + 2 charge, losing boththese electrons to form the noble gas configuration:

Ba, Z=56, Column 2A, +2 cation:

[Xe54] 6s2 - 2e[Xe54] Xenon configuration

Ba 2+

Column 2A: All Ions, +2

Be Z=4 He2 2s2 Be 2+ He2

Mg Z=12 Ne10 3s2 Mg 2+ Ne10

Ca Z=20 Ar18 4s2 Ca 2+ Ar18

Sr Z= 38 Kr36 5s2 Sr 2+ Kr36

Ba Z= 56 Xe54 6s2 Ba 2+ Xe54

Ra Z= 88 Rn86 7s2 Ra 2+ Rn86

In the p block, elements filling the p subshell, bothcations and anions are formed: let’s consider thecations first...

Aluminum, in group 3A, loses outer s and p electrons to form a + 3 cation:

Other metals in the p block show variable charges,losing either the p e’s only or the p’s and s’s

Al, Z=13, Column 3A, +3 cation:

1s2 2s2 2p6 3s23p1-3e

1s2 2s2 2p6 Neon configuration

Al3+

P Block metals: Variable Charges

Tl Z=81 Xe544f145d106s26p1 Tl 1+ Xe544f145d106s2

Tl Z=81 Xe544f145d106s26p1 Tl 3+ Xe544f145d10

Pb Z=82 Xe544f145d106s26p2 Pb 2+ Xe544f145d106s2

Pb Z=82 Xe544f145d106s26p2 Pb 4+ Xe544f145d10

Bi Z=83 Xe544f145d106s26p3 Bi 3+ Xe544f145d106s2

Bi Z=83 Xe544f145d106s26p3 Bi 5+ Xe544f145d10

Also: Ga, In: 1+, 3+; Sn, 2+, 4+; lower charges more common

Anions of the P Block

The non-metals in columns 5, 6 and 7 are most likely to form monoatomic anions; the metalloids of thesegroups are less likely to be found as these anions.

In all cases, these elements gain sufficient e’s to become “isoelectric” with following noble gas.

“ISOELECTRIC”: same number of electrons

Anions Isoelectric with Neon:

N, Z=7, Column 5A, -3 anion:

1s2 2s2 2p3+3e

1s2 2s2 2p6 Neon

configuration

O, Z=8, Column 6A, -2 anion:

1s2 2s2 2p4+2e

1s2 2s2 2p6 Neon

configuration

F, Z=9, Column 7A, -1 anion:

1s2 2s2 2p5+1e

1s2 2s2 2p6 Neon

configuration

N 3-

O2-

F1-

Anions Isoelectric with Argon:

P, Z=15, Column 5A, -3 anion:

1s2 2s2 2p6 3s23p3+3e

1s2 2s2 2p63s2 3p6 Argon

configuration

S, Z=16, Column 6A, -2 anion:

1s2 2s2 2p6 3s23p4+2e

1s2 2s2 2p63s2 3p6 Argon

configuration

Cl, Z=17, Column 7A, -1 anion:

1s2 2s2 2p6 3s23p5+1e

1s2 2s2 2p63s2 3p6 Argon

configuration

P3-

S2-

Cl1-

Let us consider the “variable charge” transition elements:these metals can utilize both their outer s and their inner d electrons for ion formation, and they are not as likely to revert to a noble gas in the process:

In forming ions, the outermost electrons, the “s” e’s, arelost first to form a +2 ion which most transition elementsexhibit. The other charges arise from subsequent loss of 1 or more d electrons.

s’s lost first, then d’s

Fe, Z=26 Column 8A, +2 cation:

[Ar18] 3d6 4s2-2e [Ar18] 3d6 Fe2+

Fe, Z=26 Column 8A, +3 cation:

[Ar18] 3d6 4s2-3e [Ar18] 3d5 Fe3+

Note that in the second cation, Fe3+, The 3d subshellconsists of 5 unpaired, same spin electrons, leadingus next to a consideration of the topic of magnetism... But first: Group Work...

GROUP WORK

Do: Short form, order of shells for atom, then for ion:

Ag, Ag+ I, I 1-

Zn, Zn 2+ Se, Se2-

Ag, Z=47: [Kr36] 4d105s1

Ag1+ : [Kr36] 4d10 Zn, Z=30: [Ar18] 3d104s2

Zn 2+: [Ar18] 3d10

I, Z=53: [Kr36] 4d105s25p5

I 1-: [Kr36] 4d105s25p6

Se, Z= 34: [Ar18] 3d104s24p4

Se2- : [Ar18] 3d104s24p6

Key:

Magnetism

Substances may be classified under this heading three ways:

a) diamagnetic: slightly repelled by a strong magnet

b) paramagnetic: attracted to a magnetic field,

c) ferromagnetic: strongly attracted to magnetic field

Most substances fall into the category of “diamagnetic”, meaning that they appear to be un-attracted to ordinary “kitchen” magnets, areare actually slightly repelled by strong magneticfields generated in the laboratory.

A significant number of metals and compounds areattracted to strong magnetic fields in the lab although they are not attracted to weak magnets of the “refrigerator” variety: they are “paramagnetic.”

On the other hand, the compounds or metals exhibiting“ferromagnetism” are used to make up ordinary household magnets and are attracted to weak and strong magnetic fields.

Examples of this type are the salt magnetite, Fe3O4, and“Alnico” an alloy of Al, Ni and Co.

The characteristic which separates compounds and elements into these categories turns out to be one that is predicted by electronic configurations: thepresence or absence of unpaired electrons in the ion or the atom...

Diamagnetism: no unpaired electrons in atom oreither ion of compound;

Paramagnetism: one or more unpaired electron inatom or either ion of compound;

Ferromagnetism: many unpaired electrons in atom oreither ion of compound.

We find unpaired electrons in the metallic elements when subshells are unfinished:

Metals in Column 1A,(s1); 3A,(s2p1) 4A (s2p2), 5A,(s2p3) are predictably paramagnetic, as well as the transitionand inner transition metals, d and f subshell fillers.

Nonmetallic elements, except oxygen, form polyatomic molecules with no unpaired e’s, all diamagnetic ).

Most compounds have no unpaired electrons and arediamagnetic as well; they have been lost, gained or shared in the bonding process. The notable exceptions are the ions of the d block metals.

Transition elements have many unpaired electrons inboth atoms and ions, and offer best structures forferromagnetism:

[Ar18] 3d5 Fe3+

Magnetite: Fe2O3:

Alnico:

Al, 2s2 2p1; p's shown

Co, Z=27, 4s23d6

Ni, Z=28, 4s23d7

Group Work

Do orbital box diagram for last subshell to be filled for the following elements, then decide which are

•“diamagnetic” (not attracted to a magnet, no unpaired e’s)• “paramagnetic” (unpaired e’s, attracted)

Cs, Ca, Cu, C, Kr

Key: Cs, Ca, Cu

Cs, Z=55: [Xe54] 6s1

6s1

paramagnetic

Ca, Z=20: [Ar18]3s2

3s2

diamagnetic

Cu, Z=29: [Ar18] 3d10 4s1

4s1

paramagnetic

Key: C, Kr

C, Z=6: [He2] 2s22p2

2p2

paramagnetic

Kr, Z=36: [Kr36]

diamagneticAll e’s paired